Set $wgJobRunRate to 0 and set up a crontab or shell script to run jobs (like this with this for example). With $wgJobRunRate at 0 and the above changes, you should be able to avoid db hits on many requests.

Set $wgDiff and $wgDiff3 to gnu diff utility (download as needed). This is recommended. The default PHP diff code is slow and crashy.

[MySQL] Set your mysql server config files to only use server modes corresponding to $wgSQLMode (default is "" for no modes). Restart the mysql server, and then set $wgSQLMode = null.

If using SQLite, there are going to be many editors working at a time, and you are willing to sacrifice SERIALIZABLE atomic transactions (key parts of MediaWiki will still use them), you can add this to the bottom of LocalSettings.php:

If using SQLite, run php maintenance/sql.php and execute PRAGMA journal_mode=WAL;.

If using SQLite with the default database job queue, move the job table to another sqlite database.

Open the current database via the sqlite3 command line utility, run .schema job, copy SQL the output, and quit (use ".quit").

Make a new empty <YOUR MEDIAWIKI SQLITE DATA DIRECTORY>/job/<YOUR DB NAME>.sqlite file and open it in sqlite3. Paste in the CREATE TABLE output from above and quit. This should create a new empty job table.